Warning: a Eurovirus pandemic is about to strike. It lasts for a paralysing six weeks, and leaves enervation and exhaustion, but it's not life-threatening. The bill to ratify the Lisbon treaty gets its second reading in the Commons on Monday and the debate lasts until March. Yesterday the key cross-party amendment was tabled calling for a referendum - the success of which depends on the size of any Labour rebellion. It was signed by 20 Labour MPs, but organiser Ian Davidson claims another 100 might vote for it. Government whips think only 20 will join Labour's lemming tendency.

No other bills will go through in this time. The place will be a morgue, with only a clutch of the living dead on their feet for hour after hour. A daily three-line whip will fray MPs' tempers, but any amendment means the whole treaty falls - here, and right across Europe. If Labour whips were caught napping, an ambush could end it all. But it won't happen. The crunch comes towards the end, over the referendum amendment, which will almost certainly fail, even though the Lib Dems will abstain and there will be Labour rebels. For weeks on end parliament will do its democratic duty, but it won't be an edifying spectacle - Britain displaying its dismal worst aspects, again.

For veterans of all the other treaties since the 1973 common market entry and the 1975 referendum, this won't be deja vu all over again. For the first time ever the Tories will be united, bar the last beleaguered few stalwarts of the Ken Clarke clan. For the first time, John Major's notorious "bastards" hold the ring with full backing from their leader and their shadow foreign secretary, die-hard William Hague. As Bill Cash and David Heathcoat-Amory rise day after day to challenge every dot and comma as they shake, rattle and roll with horror stories of Brussels abominations from straight bananas to fishermen in hairnets and the end of Our Island Story, Hague and Cameron will be nodding with sage approval.

This is a highly significant shift in Tory party history. Ted Heath took us in, Margaret Thatcher signed the Single European Act and John Major signed up for Maastricht. Even in her notorious Bruges speech, Thatcher said: "Our destiny is in Europe." That is not quite what Tory leaders say now. Under tough interrogation by Andrew Marr last Sunday, David Cameron said that even if the treaty is in force by the next election, if he were prime minister: "We will not be content to rest at that point because we think too much power would have been passed from Westminster to Brussels." That mantra he repeats - "We will not let matters rest". Pressed to say what that means, he would only offer a promise to renegotiate what cannot be renegotiated. This is fantasy politics that can't survive the furnace of an election campaign. There is not a chance the other 26 countries will agree to reopen the treaty, and he knows it. Instead they will point to clause 49A, the first getout clause in any EU treaty allowing a member to quit. The "better off out" group of his Tory MPs will point to it too. Cameron is not daft enough to say he wants out, but, as the lady used to say, There Is No Alternative.

Many Tories talk up a new, looser relationship, free-trading like Norway in the European economic area. But Norway pays dearly as a big net contributor, getting no grants in return and no seat to share in EU decision-making. Good idea? Just as the EU turns increasingly towards the British agenda, just as Nicolas Sarkozy and Angela Merkel, along with many others, represent the closest yet to Tory views, just as the EU pledges no further integration in a treaty giving power back to nation states, the Tories choose to turn more absolutely anti-European than ever before.

Labour reckons this scrupulously thorough debate will expose the Tories as friendless cranks, unfit to govern. Cameron will be embarrassed by the Cash brigade's 1,000 amendments, ranting away to an empty chamber. In all 26 member states, the Tories' only allies are Greek communists, Dutch animal rights and Sinn Féin. MPs are getting few letters on the referendum, pollsters find the public never mention it spontaneously and the Sun and the Telegraph are embarrassed by how few bothered to sign their referendum petitions. That's the way Labour whistles bravely in the dark: they should win in the Commons, but the Lords is unfathomable at present.

On the other side, Tories think their party's hour has come: the public wants a referendum, believes it was promised one and knows the government only refuses for fear of losing. But the Tories' real strength is in their press. Rupert Murdoch, Paul Dacre and the Barclay brothers have not gone away, though their recent silence before the storm is eerie. Remember the first day of Labour's party conference, when the Sun ran seven pages of referendum rant. Even if it bores readers into plummeting sales, these press barons are crazed enough not to care, so expect a daily bombardment of Euro lies. Big lies will say the creation of an EU foreign affairs minister means Britain will lose its UN seat. Other lies say we will be forced to give criminals the vote, 21-gun salutes will be muffled, children's swings, walnuts and wood-burning stoves will be banned, yoghurt will be relabelled Fermented Milk Pudding, and UK places will be renamed. All these are already in print.

Out of fear and populism, Labour never sold voters the value of the EU - and Gordon Brown was the most truculent. Ministers took praise for popular EU actions but blamed "Brussels" for tough EU decisions. However, Brown made his first wholeheartedly pro-European speech this week, and in David Miliband Labour has a genuine enthusiast as foreign secretary: his recent speech in Bruges was a landmark corrective.

Now, backs to the wall, there is nothing for it but for Labour to sell Europe hard in the coming weeks. Jim Murphy, the Europe minister, who speaks many languages, has prepared more than a million words to prove his own enthusiasm. To make sense of these days of parliamentary agony, there will be clear themes, and other ministers will take to the dispatch box. Ed Balls will point out that all the big children's organisations are backing the treaty: their statement calls it a positive step as it includes children's rights. Hilary Benn will stand up with the support of the environmental groups who see the EU as key to climate action. Douglas Alexander will speak with support from Oxfam and the other aid organisations for the treaty's "potential for a stronger poverty focus". It's brave and honest of all these NGO umbrella organisations to join this fight. They see qualified majority voting as no loss of British sovereignty but the only hope of action that can otherwise be blocked by any one of 27 countries.

The treaty will almost certainly pass in the Commons, so it would be foolhardy for the unelected Lords to wreck it. The public will be bored to tears and sketch writers may take sick leave, but Labour on its feet making a stand will at last persuade itself once and for all of the value of the EU. Meanwhile, it leaves the Tories with an impossible policy that leads only to the EU exit door.